High saturated fat diets damage liver, increase fat cell size, cause fat to be stored in liver and muscles

  •  High fat diets are very popular these days but unfortunately they do not distinguish between saturated and unsaturated fat.
  • Furthermore, quite a lot has been written about the ratio of omega-6 to omega-3. Basically, the higher the ratio, the more unhealthy is the diet, due to the inflammatory potential of too much omega-6 in relation to omega-3.
  • A recent paper has now shown that between two high fat diets with the same calories and the same ratio of omega-6 to omega-3, the one that contains mainly saturated fat is much worse than the one that contains mainly poly-unsaturated fat (PUFA).
  • Specifically, a high fat diet rich in saturated fat for six months leads to increased adipocyte (fat cell) size, liver damage, and "ectopic" fat storage in liver and muscle. None of these changes have been observed with a high fat diet rich in poly-unsaturated fat.
  • No differences were found between the two diets in body weight, total adiposity (total fat levels), adipose tissue health, adipokines (fat tissue hormones), whole body energy balance or glucose tolerance.
  • In summary, based on the findings of this study, if you are going to embark on a high fat diet, forget saturated fat coming from meat, cheese, milk, butter, chocolate etc and focus on avocados, nuts, seeds, olive oil, flax/chia seeds, oily fish and coconut oil (coconut oil saturated fat is "different", as it gets metabolised for energy than for fat storage).
  • Source: A Difference in Fatty Acid Composition of Isocaloric High-Fat Diets Alters Metabolic Flexibility in Male C57BL/6JOlaHsd Mice
  • Abstract: Poly-unsaturated fatty acids (PUFAs) are considered to be healthier than saturated fatty acids (SFAs), but others postulate that especially the ratio of omega-6 to omega-3 PUFAs (n6/n3 ratio) determines health. Health can be determined with biomarkers, but functional health status is likely better reflected by challenge tests that assess metabolic flexibility. The aim of this study was to determine the effect of high-fat diets with different fatty acid compositions, but similar n6/n3 ratio, on metabolic flexibility. Therefore, adult male mice received isocaloric high-fat diets with either predominantly PUFAs (HFpu diet) or predominantly SFAs (HFs diet) but similar n6/n3 ratio for six months, during and after which several biomarkers for health were measured. Metabolic flexibility was assessed by the response to an oral glucose tolerance test, a fasting and re-feeding test and an oxygen restriction test (OxR; normobaric hypoxia). The latter two are non-invasive, indirect calorimetry-based tests that measure the adaptive capacity of the body as a whole. We found that the HFs diet, compared to the HFpu diet, increased mean adipocyte size, liver damage, and ectopic lipid storage in liver and muscle; although, we did not find differences in body weight, total adiposity, adipose tissue health, serum adipokines, whole body energy balance, or circadian rhythm between HFs and HFpu mice. HFs mice were, furthermore, less flexible in their response to both fasting- re-feeding and OxR, while glucose tolerance was indistinguishable. To conclude, the HFs versus the HFpu diet increased ectopic fat storage, liver damage, and mean adipocyte size and reduced metabolic flexibility in male mice. This study underscores the physiological relevance of indirect calorimetry-based challenge tests.